Controlled motion system having an improved track configuration

ABSTRACT

A transport system comprising linear motor modules utilized both straight and curved track modules, with movers displaced on the track modules by control of power applied to coils of the modules. Curved track modules have modified spline geometries to provide desired acceleration and jerk characteristics. The modified spline geometries may be defined by more than one generators, such as an equation generator and a spline fit between the equation-generated segment and one or more constrained points or locations. The curved track modules may be divided into 180 degree modules, or may be reduced to 90 degree, 45 degree or other fractional arcs to provide for modular assembly, mirror-image geometries and motion profiles, and the like. The system may be adapted to provide improved motion characteristics based on modification of a conventional spline geometry.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional patent application of U.S.Provisional Patent Application No. 61/821,450, entitled “ControlledMotion System Having an Improved Track Configuration”, filed May 9,2013, which is herein incorporated by reference.

BACKGROUND

The present invention is directed to linear motor and transport systems,and, more particularly, to arrangements for providing curves anddirectional transition modules in such systems.

BRIEF DESCRIPTION

Transport systems, such as controlled motion systems utilizing lineardrives, are used in a wide variety of processes (e.g. packaging,assembly automation, processes involving use of machine tools, etc.) andprovide the advantage over conventional rotary drive systems ofincreasing both the speed and the flexibility of the process. Inparticular, linear motors operate as magnetic drives creating a changingmagnetic field to directly transport the axis or transport element alonga defined track, thereby eliminating various conventional axes, such asgear heads, shafts, keys, sprockets, chains and belts, used withtraditional rotary drive systems. The reduction of mechanical complexityover rotary drive systems provides both reduced cost and increased speedcapability by virtue of reduced inertia, compliance, damping, frictionand wear. Further, controlled motion systems utilizing linear drivesalso provide greater flexibility than conventional rotary drive systemsby allowing one or more individual axes or transport elements to beindependently controlled while transporting articles along an entiretrack.

Unlike conventional rotary drive systems that have a single drive andtypically a single rotary motor for energizing an axis or transportelement for moving articles along a track, linear motion systemstypically comprise interconnected track sections wherein one or moredrives are electrically coupled to a plurality of transport elements andhave individually controlled coils that cooperate with one or morecontrol units to energize or de-energize the coils to create magneticfields effective for providing controlled motion of each transportelement traveling along the track. Such systems also employ sensors,such as linear encoders spaced at fixed positions along the track andsensors mounted on each transport element that cooperate with the linearencoders to provide signals to a control unit for use in determining theposition of each transport element along the track.

Linear motion systems typically have tracks comprising straightsections, and where loops or more complex layouts are desired, curvesections. One problem associated with such tracks is encountered whenthe curvature of the track changes suddenly, such as when going from astraight part of the track to a curved part of the track. This resultsin the transport element experiencing a high rate of acceleration andjerk, particularly at the point of transition between straight andcurved sections (and vice versa). Such abrupt changes can result inhigher required motor forces, positional errors, cogging, commutationissues, and other undesirable effects on motion and control. Certainsystems have adopted “spline” curves to ease some of these transitionaleffects, but such shapes are often less than optimal from the point ofview of space utilization, envelope dimensions, flexibility in motionand force design, and so forth.

There is a need, therefore, for track assemblies and designs forcontrolled motion system having straight sections and curved sectionswhereby the acceleration and jerk experienced by a transport elementtraveling from a straight section of the track to a curved sectionand/or from traveling from a curved section to a straight section,and/or from traveling from a first curved section to a second curvedsection are reduced and optimized.

BRIEF DESCRIPTION

The disclosure sets forth a controlled motion system comprising a trackassembly having a straight track module and a curved track moduleinterconnected to form a continuous track, each module comprising aplurality of individually controlled electromagnet coils effective forcreating electromagnetic fields. A mover is mounted for movement alongthe track and having magnetic reaction elements positioned that interactwith the fields. The curved track module comprises a modified splinegeometry comprising at least two different generators.

The disclosure also relates to controlled motion system comprising acurved track module interconnectable with other track modules to form acontinuous track and comprising a plurality of individually controlledelectromagnet coils effective for creating electromagnetic fields fordisplacing a mover along the curved track module, wherein the curvedtrack module comprises a modified spline geometry comprising at leasttwo different generators.

Still further, the disclosure relates to a controlled motion systemcomprising a curved track module interconnectable with other trackmodules to form a continuous track and comprising a plurality ofindividually controlled electromagnet coils effective for creatingelectromagnetic fields for displacing a mover along the curved trackmodule; wherein the curved track module comprises a modified splinegeometry comprising multiple generators, and wherein the curved trackmodule comprises a 90 degree module with a modified spline geometry thatis symmetrical about a 45 degree centerline.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1A is a perspective view of an exemplary transport systemillustrating straight and curved track modules and several moverspositioned for movement along the modules;

FIG. 1B is a top view of a similar transport system in which motor coilsare positioned differently than in the system of FIG. 1A;

FIG. 2 is a diagrammatical representation of the system of FIGS. 1A and1B;

FIGS. 3A-3C are top views of exemplary alternative layouts for suchsystems, utilizing both straight and curved track modules;

FIG. 4 is a schematic representation of a portion of a prior art curvedtrack module of a track assembly having a generally constant radiustrack geometry;

FIG. 5 is a graphical representation of linear acceleration of an objecttraveling from a straight track module to and along the curved trackmodule of FIG. 4;

FIG. 6 is a schematic representation of a portion of a curved trackmodule of a track assembly having a modified spline smoothed curve trackgeometry;

FIG. 7 is a graphical representation of linear acceleration of an objecttraveling from a straight track module to and along the curve trackmodule of FIG. 6 of the track assembly;

FIG. 8 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 6;

FIG. 9 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 10 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvedtrack module of FIG. 7 of the track assembly;

FIG. 11 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 9;

FIG. 12 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 13 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvedtrack module of FIG. 12 of the track assembly;

FIG. 14 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 12;

FIG. 15 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 16 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvetrack module of FIG. 15 of the track assembly;

FIG. 17 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 15;

FIG. 18 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 19 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvetrack module of FIG. 18 of the track assembly;

FIG. 20 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 18;

FIG. 21 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 22 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvetrack module of FIG. 21 of the track assembly;

FIG. 23 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 21;

FIG. 24 is a schematic representation of a portion of a curved trackmodule of a track assembly having another modified spline smoothed curvetrack geometry;

FIG. 25 is a graphical representation of linear acceleration of anobject traveling from a straight track module to and along the curvetrack module of FIG. 24 of the track assembly;

FIG. 26 is a schematic representation graphically depicting curvature ofthe curved track module of FIG. 25;

FIG. 27 is a schematic illustration showing of a portion of a curvedtrack module of a track assembly having a modified spline smoothed curvetrack geometry; and

FIG. 28 is a top view of a motor stator section for a portion of thecurved track module of FIG. 27.

DETAILED DESCRIPTION

Turning now to the drawings, and referring first to FIG. 1A, a transportsystem 10 as illustrated for moving articles or products around a track12. As will be appreciated by those skilled in the art, in manyapplications, the transport system will be configured to inter-operatewith other machines, robots, conveyers, control equipment, and so forth(not separately shown) in an overall automation, packaging, materialhandling or other application. The transport system itself generallycomprises a “linear motor” system as discussed below, in which themoving components are positioned, accelerated, decelerated, andgenerally moved under the influence of controlled magnetic andelectromagnetic fields. In the illustrated embodiment, the track 12comprises straight track modules 14 and curved track modules 16. Thesemodules may be generally self-contained and mountable in variousphysical configurations, such as the oval illustrated in FIG. 1A. Itshould be noted that other configurations are equally possible asdiscussed below. The configurations may form closed loops of variousshapes, but may also comprise open-ended segments. The system furthercomprises one or more movers 18 which are mounted to and movable alongthe track. Again, the position, velocity, acceleration, and higher orderderivative parameters are controllable for these movers by appropriatecontrol of the coils of the system that are energized and de-energizedas discussed below. In the illustrated embodiment, the movers 18interact with stationary elements in and around an outer periphery 20 ofthe track modules, although other configurations are envisaged. A sensorsystem 22 is provided to detect positions of the movers around thetrack, and such center systems may comprise permanent magnets, energizedcoils, Hall effect sensors, or any other suitable devices. In general,one component of the sensor system will be mounted on the movers, whileanother component will be mounted at fixed locations around the track.

Each mover further comprises a mounting platform 24. In an actualimplementation, various tools, holders, support structures, loads, andso forth may be mounted to this mounting platform. The movers themselvesmay be configured differently from those shown in order accommodate thevarious loads. While a horizontal configuration is illustrated in FIG.1A, other orientations may also be provided, such as ones in which theillustrated oval is generally stood on a side or end, or at any anglebetween.

The system further comprises circuitry for controlling a movement of themovers. In the embodiment illustrated in FIG. 1A, this circuitryincludes a drive circuitry 26 that provides signals to each trackmodule, and specifically individual coils (see below) of the trackmodules to create electromotive forces that interact with magnets on themodules to drive the modules to specific locations, and at specificvelocity, accelerations, and so forth. This drive circuitry maytypically include inverter circuitry that makes use of power electronicswitches to provide drive power to the individual coils of each modulein a controlled manner. In some embodiments, the drive circuitry may beincluded in each individual module, and signals provided to the drivecircuitry by power and control circuitry 28. This power and controlcircuitry (and the drive circuitry) may receive feedback from the moversand/or from the sensor system to detect the location, velocity,acceleration, and so forth of each mover. In certain embodiments themovers may also be configured to be recognized by the power and controlcircuitry 28 as individual axes that are independently controlled, butwith regulation of their position, velocity and acceleration to avoidconflicts, collisions, and so forth. The particular motion profileimplemented by the power and control circuitry 28 will typically beconfigured and implemented upon the design and commissioning of thesystem, here again, depending upon the particular task to be performed.Finally, various remote control and/or monitoring circuitry 30 may beprovided and this circuitry may be linked to the system by one or morenetworks 32. Such remote circuitry may generally allow for coordinationof the operation of the transport system with other automationcomponents, machine systems, manufacturing and material handlingmachines, and so forth.

FIG. 1B illustrates an alternative configuration for a similar transportsystem. However, in this configuration, rather than motor coils beingpositioned around the periphery of the system, coils are positionedaround the top of the system, in a generally planar arrangement. Magnetassemblies of each mover 16 face these coils and are spaced from thecoils by a small air gap. Straight and curved track modules areassembled, as above, to form an oval, although other shapes and layoutsmay be formed. The curved track modules may be adapted with modifiedspline geometries, as in the case of the system shown in FIG. 1A, and asdescribed in greater detail below.

FIG. 2 is a diagrammatical representation of the transport systemshowing one track module 36 and one mover 18 positioned along the trackmodule. The track module illustrated in FIG. 2 may be a straight orcurved track module, these two differing in their physicalconfiguration, and certain of the actual characteristics owing to thecurved nature of the curved modules as discussed below. In general,however, each mover comprises a magnet array 38 on which a number ofmagnets 40 are mounted. These will typically be permanent magnets andare mounted such that a small air gap is provided between the magnetsand coils of the track module described below. As shown in FIG. 2, thetrack module 36 further comprises a sensor component 42, such as apermanent magnet. It should be noted, however, that the particularsensor component included in the track module will depend upon thenature of the sensing strategy, the sensing resolution, the position ofthe sensor on the mover (and cooperating components on the trackmodule), and so forth. The platform 44 is provided on the mover whilemounting tools and the like as discussed above. Finally, bearings andassociated components (e.g., rollers) are mounted to the mechanicalstructure of the mover and serve to interact with one or more rails, asindicated by reference numerals 46 and 48, respectively. These bearingsand rails allow the mover to remain securely attached to the trackmodules while allowing relatively free movement of the movers along thetrack modules and supporting mechanical loads and forces encounteredduring motion.

The track module 36 will typically include a series of parallel coils 50that are associated with a stator or armature 52. In currentlycontemplated embodiments, these coils are mounted into slots in thestator, and the stator itself may be made of magnetic material formedinto a stack of laminates and structured to allow for mounting withinthe track module housing. Particular configurations, magnetic, mountingstructures and the like of the coils and stator components are generallybeyond the scope of the present disclosure. Drive circuitry 54 may beincluded in each module as discussed above to allow for controlled powersignals to be applied to the coils in order to drive and position themovers appropriately around the track module. Finally, a sensor array 56is provided in each track module to allow for interaction with thesensor components of the movers. This sensor array will typicallyprovide feedback that can indicate the position of the movers, and canbe used to derive velocity, acceleration, jerk and other motionparameters. In the illustrated embodiment a plurality of track modulesmay be mounted end-to-end and interconnected with one another and/orwith the power and control circuitry to received signals used to powerthe coils.

As will be appreciated by those skilled in the art, track modules, alongwith the magnet arrays of the movers, will generally form what may beconsidered a linear motor system. That is, electromotor force isgenerated by the controlled fields of the coils and interaction betweenthese fields and the magnetic fields of the magnet array serve to drivethe mover into desired positions, at desired speeds, and so forth. Asnoted above, these coils and the linear motor itself may be designed inaccordance with various configuration strategies, such as ones havingthe coils arranged around a periphery of the track modules, ones inwhich the coils are generally planar (in a top or bottom position of themodules), and so forth. Although the “linear” motor system may be usedin the present disclosure, it should be appreciated that curved modulesin various configurations are intended to be included under this rubric.

In addition to the configurations shown in FIGS. 1A and 1B, variousother physical layouts may be employed, such as those shown in FIGS. 3A,3B and 3C. FIG. 3A illustrates a transport system having an ovalconfiguration 58. Here the configuration is made of several straightmodules 60 and end modules 62 that form 180 degree curves. Any number ofstraight modules may be provided, and as described more fully below, thecurved modules may be provided in a single unit forming 180 degrees toclose the oval or in smaller units of 90 degrees, 45 degrees, 30degrees, and so forth. As shown in FIG. 3B, square configurations 64 maybe similarly formed by insertion of straight modules 66 between 90degree modules 68. In the rectangular configuration 70 of FIG. 3C,straight modules 72 are inserted between 90 degree modules 74, with adifferent number of straight modules on each side to form a generallyrectangular configuration. Other configurations may include variousturns, interior and exterior curves, S-shapes, open-ended tracksections, and so forth.

It should also be noted that a number of different coil and magnetconfigurations may be employed with the innovations summarized in thepresent disclosure. These may include, for example, the peripheral coiland facing magnet arrangements discussed above, and the generally planarcoil arrangements with facing magnet arrangements also discussed above.Other arrangements may include opposing coils and/or magnets, with thecooperating magnets/coils in facing relation, T-shaped magnet and/orcoil structures, and so forth.

As discussed in greater detail below, the curved track modules of thetransport system are configured with a modified spline geometry thatallows for improved control of acceleration, jerk, general movement ofthe movement of the movers around the curved sections, and so forth.Certain prior art systems included curved track modules as illustratedin FIG. 4. These curved track modules 76 have a generally constantradius geometry 78 from an entry end to an exit end. Owing to the suddenchange from a straight module to this constant radius geometry, a suddenand very high rate of acceleration and jerk were encountered asindicated in the graphical representation of FIG. 5. FIG. 5 illustratesthe acceleration and/or jerk along a vertical axis 84 plotted againsttime along axis 86. The sudden high rate of acceleration and jerk asindicated by reference numeral 88 corresponds to the transition betweenthe straight track module and the constant-radius curved-track module.Thereafter, acceleration and jerk where are generally steady asindicated by reference numeral 90, followed by a rapid change(deceleration) indicated by reference numeral 92. Such changes mayadversely affect performance of the system, and particularly may requirehigher motor forces, and in part higher loads on the movers, tracks,rails, loads, and so forth.

As provided by the present disclosure and through various alternativeconfigurations discussed below, the curved track modules have modifiedspline configurations that deviate from the constant radius geometriesof the prior art. As will be appreciated by those skilled in the art, aspline, as used in the present context, may comprise variousnon-constant radius geometries, such as cubic splines, Euler curves,clothoid curves, and so forth. More particularly, in certain embodimentsdisclosed, the modification of the spline is accomplished by combinationof two or more curve geometries, such as a cubic parabolic shape with afit spline transition. The term “modified” is intended to convey thatthe spline geometries are not simply single-equation clothoid, Eulercurves, or any single spline geometry, but are modified to providecontrolled curvature, acceleration, jerk, and other motion parameters.In particular, the modified splines described may allow for controlledentry into the curved modules, controlled exit, controlled accelerationsand jerks between the entry and exit, flattened sections that approachor equal a straight transition to allow for symmetry about a 90 degreecenterline, about a 45 degree centerline, and so forth. The modifiedsplines may also allow for flattening at end regions of a looped trackto permit reduced footprint and envelope dimensions overall.

In certain embodiments described below, at least two generators areutilized for defining the modified spline geometries. By “generator” isintended the mathematical or algorithmic basis for defining the shape ofthe spline. For example, some of the embodiments may be at leastpartially based on a cubic parabolic equation, a clothoid equation, orany other equation-based shape generator. Other segments of the splinemay be based on other, different equations, while some may be based onspline “fits” between constrained points, slopes, tangents, contours,curvatures, and so forth. In some embodiments, for example, an equationgenerator (such as a cubic parabolic equation) may be used to initiateand/or end the spline geometry, while a fixed point or location may beused to perform a spline fit between a selected end location of theequation-generated segment and the fixed point or location. In manyapplications, moreover, it may be useful for the fit segment to conformto particular arc length constraints, overall envelope dimensions, andso forth. Motion profiles resulting from the modified spline geometriesmay also be considered as constraints in the modification. Otherconstraints may include, for example, the layout and design of bearingsand rollers of the movers (e.g., movement of the center of mass of themovers will typically differ from the movement of each bearing or rollerowing to the spacing and position of the bearings and rollers, thelayout of guide rails located adjacent to the track modules, and soforth).

FIGS. 6, 7 and 8 illustrate a first modified spline configuration andcharacteristics associated with it. In this configuration, the curvedtrack module 94 has a modified spline geometry 96 from an entry end toan exit end 100. It should be noted, however, throughout the presentdisclosure, that the terms “entry” and “exit” are somewhat arbitraryinsomuch as the mover may enter from one direction and exit from theother, or in a contrary fashion, movers may be controlled to move inopposite direction. The modified spline geometry 96 shown in FIG. 6generally corresponds to a clothoid curve, but that has been flattenedtoward the exit end 100 to allow for control of the overall envelope orlengthwise dimension of a turn. It may also be noted that the curvedtrack module 94 generally forms only half of a 180 degree turn. Similargeometries, including modified (flattened) splines may be formed forfull 180 degree turns, or for any fractional angular turn in the module.As illustrated in FIG. 7, the acceleration or jerk 102, plotted along atime axis 104 allows for a more gradual onset or acceleration 106 and amore gradual deceleration 108 entering and exiting the turn, with acontrolled profile 110 therebetween. (Note that the graphicalrepresentation of FIG. 7, and of similar figures discussed belowactually represent acceleration, while jerk is simply the slope (nextderivative) of this acceleration profile. Also note that the graphicalrepresentation of FIG. 7, and again of similar figures discussed below,is for a 180 degree turn, with the evident symmetry resulting fromside-by-side placement of self-similar or mirror image 90 degree moduleswith smooth transitions at the point of mating.) The more gradualacceleration and jerk are caused by the curvature illustrated in FIG. 8.This curvature 112 here is shown with the modified spline shape as abasis for lines of curvature radiating outwardly indicating the degreeof curvature. The initiation (or completion) of the curvature asindicated by reference numeral 114 corresponds to the transition betweenthe straight section (e.g., and adjacent straight track module) and aboundary curvature 116 which causes the acceleration (or decelerationdepending upon the direction of movement) of the mover. Thereafter, thecontrolled spline curvature 118 allows for control of the accelerationand jerk corresponding to the controlled profile 110 of FIG. 7. Byflattening, shaping, or otherwise deviating from the constant-radiusgeometry and from the conventional clothoid geometry, specificacceleration and jerk profiles, and corresponding performance may beobtained.

FIGS. 9, 10 and 11 illustrate a second alternative modified splineconfiguration and corresponding performance parameters. The curve trackmodule 120 here has a second modified spline geometry 122 from an entryend 124 to an exit end 126. Here further modification of the curvaturehas been made to further control the acceleration and jerk profiles seenby a mover. The acceleration and jerk 128, plotted along time axis 130illustrated in FIG. 10 here provide for a more gradual acceleration 132followed by a more gradual deceleration 134 and a controlled profile 136therebetween. The further modification of the spline here allows for aninflection near the upper end of the acceleration portion of the profile(near the top of the generally linear acceleration 132) and acorresponding inflection or change for the deceleration 134. Thecontrolled profile 136 may allow for deceleration between the ends, withacceleration and other controlled movement therebetween. It can also beseen that this profile has been altered from that shown in FIG. 7 by asomewhat more steep deceleration following the initial acceleration, asomewhat more steep acceleration prior to the exit end, and so forth.These motion characteristics provided by the curvature 138 illustratedin FIG. 11. Here the initiation (or completion) of the curvature 140allows for a somewhat more smooth transition or boundary curvature 142as compared to that of FIG. 8. Thereafter, the modified spline allowsfor somewhat reduced curvature in the controlled spline curvaturesection 144. Such curvature and modification can be designed to providefor smoother ramps of acceleration and jerk, and smoother or certaindesired movement characteristics around the turn.

A third modified spline geometry as illustrated in FIG. 12 withperformance characteristics illustrated in FIGS. 13 and 14. Here thecurved track module 146 has a modified spline geometry 148 between anentry end 150 and an exit end 152. The resulting acceleration and jerk154, plotted at along time axis 156 provide for an even more gradualacceleration and jerk 158 and an even more gradual deceleration and jerk160, with a controlled profile 162 therebetween. Here again, theacceleration and jerk result from the curvature 164 of the modifiedspline geometry from the initiation (or completion) point 166 through acurvature ramp 168, followed by the controlled spline profile 170.

A further example of such modified splines is illustrated in FIGS. 15,16 and 17. Here, the curved track module 172 has a modified splinegeometry 174 from an entry end 176 to an exit end 178. As shown in FIG.16, the acceleration and jerk 180, plotted against time 182 provides fora gradual acceleration 184 and a gradual deceleration 186 with a moreflattened controlled profile 188 therebetween. Here again, thedeceleration, motion profile, and acceleration provided in thecontrolled profile segment can be modified by adapting the curvature 190as indicated in FIG. 17. The curvature here again begins to deviate fromthe straight segment at the initiation (or completion) point 192,followed by boundary curvature 194 and the controlled spline curvature196.

A further or fifth modified spline configuration is illustrated in FIG.18, along with its performance characteristics shown in FIGS. 19 and 20.Here the curved track section 198 has a modified spline geometry 200from an entry end 202 to an exit end 204. The spline geometry 200 hasbeen modified to provide an acceleration and jerk 206 against time 208that is somewhat more aggressive an acceleration 210 and an deceleration212, with an even more controlled profile section 214 therebetween. Hereagain, the curvature 216 affords this behavior from an initiation (orcompletion) point 218, through a boundary curvature 220 and thecontrolled spline curvature 222.

The modified splines illustrated in FIGS. 15 and 18 result from thecombination of at least two different generators for the splinegeometry. In particular, these two configurations transition between acubic parabola curve at the onset of the curved track module to a fitspline at a transition point. The cubic parabola section will generallycorrespond to the accelerations and decelerations illustrated in FIGS.16 and 19, with the fit section corresponding to the deceleration andother performance parameters therebetween. It may also be noted thatthese geometries include a segment of constant radius as indicated bythe horizontal portion of the controlled profile segments indicated nearthe centers of FIGS. 16 and 19. In practice, such techniques may beutilized to modify the spline geometries to fit the overall envelope ofthe curves to desired constraints as with the flattened splinesdiscussed above. Moreover, transitions of this type may be used to allowfor the design of 90 degree curves that mate with one another and thatare generally self-similar about a centerline. Similar splinemodifications may be used for symmetrical transitions between 45 degreesections, 30 degree sections and any desired fractional curve.

As will be appreciated by those skilled in the art, the ability toaccommodate specified envelope dimensions by adaptation of a modifiedspline geometry, and particularly one defined by multiple generators, isextremely useful in many applications. That is, even if a splinegeometry, such as a clothoid shape, were used to define a curve or turnin such systems, the overall dimensions dictated by the full clothoidshape may constrain the other dimensions of the track layout. Forexample, to fully respect the geometry of an unmodified clothoid (orother spine shape), the length of the curved module(s), the spacingbetween the straight modules that join to the curved modules to form aloop or other shape will be constrained by the dimensions imposed by thecurve shape. The present modified spline configurations allow forenvelope dimensions to be specified, and the curved modules engineeredwith multiple generators to optimize or compromise performance with thespace constraints and envelope dictates of the application.

FIG. 21 illustrates a curved track module 224 having a further modifiedspline geometry 226. Here the track module is illustrated as completinga 180 degree turn from an entry end 228 to an exit end 230. The splinehere is modified to transition between a straight section at the entryend 228 to a further straight section near the exit end 230, with agenerally symmetrical motion profile therebetween. As indicated by thegraphical representation of FIG. 22, the acceleration and jerk 232,plotted against time 234 indicate an acceleration 236 followed by adeceleration 238 near the center of the 180 degree turn. Thereafter, asubstantially identical acceleration 236 is seen followed by a similardeceleration 238 near the exit end. Therebetween, controlled profiles240 indicate inflected or bent accelerations and jerks that are providedby the combination of more than one generator for the spline. In thisparticular example, a cubic parabola at the entry and exit istransitioned to a fit spline between the entry and the midpoint of the180 degree turn, with an identical cubic parabola being fit around themidpoint. This modified geometry provides the symmetrical accelerationand jerk characteristics illustrated in FIG. 22. The correspondingcurvature 242 shown in FIG. 23 exhibits an initiation (or completion)244 followed by a boundary curvature 246 and a controlled splinecurvature 248. By allowing for the generally symmetrical geometry andcorresponding motion profiles, the curved track modules may be made in180 degree arrangements, or may be split about a centerline 254 (seeFIG. 21) in which a first 90 degree module 250 is mated with amirror-image 90 degree module 252, each having similar geometries andmotion profiles. Here again, the modification of the spline geometryallows for control of these motion profiles, control of acceleration andjerk, control of loads and motor forces, and so forth.

A further modified spline geometry is illustrated in FIG. 24 for acurved track module 256. The modified spline geometry 258 is hereillustrated as forming a 180 degree curve from an entry end 260 to anexit end 262. Here again, the illustrated modified spline includes morethan one generator, and in this case another cubic parabola near theentry and exit ends, transitioning to a fit spline therebetween, with afixed constraint around a midpoint of the 180 degree curve. Thisconfiguration, and the previous modified spline may be thought of as a“straight-to-curved-to-straight” geometry from the ends 260 and 262 tothe center point of the 180 degree curve. The motion profile,particularly the acceleration and the jerk 264 plotted against time 266as illustrated in FIG. 25 is generally similar to that of the previousembodiment with accelerations 268, decelerations 270, bends orinflections in these accelerations and decelerations, with controlledprofiles 272 therebetween. This profile is again the result of thecurvature 274 illustrated in FIG. 26 from the initiation (or completion)point 276 through the boundary curvature 278 to the controlled profile280. Such modified splines may be generated by inputting the initialgenerator, such as the cubic parabola, which may also form the exit tothe geometry. A point therebetween may be fixed as a constraint, withthe spline being fitted between the end of the first generator and thefixed point or points.

As in the previous embodiment, this configuration may allow formirror-image modules 282 and 284 as illustrated in FIG. 24, which areassembled about a centerline 286 with a smooth transition therebetween.A single portion of the module is illustrated in FIG. 27 as indicated byreference numeral 288. Reference numeral 288 may correspond to a housingor mounting structure that has a generally constant radius outerparameter 290 for receiving a motor stator or armature as illustrated inFIG. 28. As will be appreciated by those skilled in the art, the stator292 may be formed of a plurality of magnetic sheets or laminates thatare assembled to provide the desired magnetic and mechanical structures.Such laminates may be stamped and assembled, with any further machiningperformed prior to or after assembly. In this particular implementation,a circular mounting surface 294 is formed by stator laminates to allowfor ease of mounting on the housing 288 of FIG. 27. The spline geometryis provided by the outer portion of the stator as indicated by referencenumeral 296. The laminates here are formed to provide coils slots 298.These slots may be positioned to maintain desired spacings, desiredoverall arc lengths, and so forth in a consistent manner with thestraight modules and any other curved modules of the system. It may alsobe noted that this particular configuration may allow for utilization ofthe same laminates, same stators, and same modules for one or morecurved sections, with these either being simply moved to anotherposition or flipped for mounting to provide the geometries and motionprofiles discussed above. Moreover, in the embodiment illustrated inFIG. 28, the stator is symmetrical about a 45 degree symmetry line asindicated by reference numeral 300. This particularly may allow forflipping or repositioning of the same mechanical component for use in 90(or fractional) degree segments. Similar symmetries may be provided atother angles, such as 30 degrees, 15 degrees, and so forth.

As discussed above, more than one generator may be used for some or allof the modified splines disclosed, and often one of these will be anequation that defines segment of the geometry, while another is a fitbetween this segment and one or more constrained points, arc lengths,and so forth. Optimized curves may thus be generated by creating anequation driven curve to define the lead-in geometry to control the jerkand acceleration at the transition from the straight to the curve. Thelead-in segment (and the lead-out segment) may be, for example definedby cubic parabola functions. The remaining portion of the modifiedspline may transition from the endpoint of the equation-driven segmentto a diameter that results in the correct motor length (or arc length,such as 400 mm at a 2.5 mm offset trace, currently 262.35 mm).

In some embodiments, a transition spline segment is made equal curvatureand tangent at a transition point from the equation driven curve, andboth curves are perpendicular to construction lines at the start and endof the curves. The tangent vector dimension (e.g., 160 mm), in acurrently contemplated embodiment, was found iteratively by evaluatingthe curvature of the splines. The goal was to have the largest minimumradius of curvature in the transition region while maintaining as closeas possible a consistent rate of change of curvature at the transitionfrom the equation driven spline to the transition spline. Thedenominator of the equation driven spline curve can be increased inorder to flatten the curve (reduce the rate of change of curvature).When the length is increased, the denominator may be increased tomaintain the same rate of change of curvature.

While only certain features of the present disclosure have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the disclosure.

1. A controlled motion system comprising: a track assembly having astraight track module and a curved track module interconnected to form acontinuous track, each module comprising a plurality of individuallycontrolled electromagnet coils effective for creating electromagneticfields; and a mover mounted for movement along the track and havingmagnetic reaction elements positioned that interact with the fields;wherein the curved track module comprises a modified spline geometrycomprising at least two different generators.
 2. The controlled motionsystem of claim 1, curved track module comprises a modified splinehaving an equation-generated segment and a transition-generated segmentwith a smooth transition therebetween.
 3. The controlled motion systemof claim 2, wherein the equation-generated segment comprises a clothoidcurve.
 4. The controlled motion system of claim 2, wherein theequation-generated segment comprises a cubic parabolic curve.
 5. Thecontrolled motion system of claim 1, wherein the modified splinegeometry comprises a flattened region around a centerpoint of a 180degree curve.
 6. The controlled motion system of claim 1, wherein thecurved track module comprises a 90 degree curve.
 7. The controlledmotion system of claim 1, wherein the curved track module comprises twoself-similar, mirror image modules positioned side-by-side.
 8. Thecontrolled motion system of claim 7, wherein each curved track modulecomprises a 90 degree curve.
 9. The controlled motion system of claim 1,wherein the curved track module comprises a 90 degree module with amodified spline geometry that is symmetrical about a 45 degreecenterline.
 10. The controlled motion system of claim 1, wherein each ofthe straight and curved track modules comprises drive circuitry forcontrolling movement of the mover along the track assembly byenergization of the coils.
 11. The controlled motion system of claim 1,wherein the electromagnetic coils are provided around a periphery of themodules.
 12. The controlled motion system of claim 1, wherein theelectromagnetic coils are provided generally in a plane near a top orbottom surface of the modules.
 13. A controlled motion systemcomprising: a curved track module interconnectable with other trackmodules to form a continuous track and comprising a plurality ofindividually controlled electromagnet coils effective for creatingelectromagnetic fields for displacing a mover along the curved trackmodule; wherein the curved track module comprises a modified splinegeometry comprising at least two different generators.
 14. Thecontrolled motion system of claim 13, curved track module comprises amodified spline having an equation-generated segment and atransition-generated segment with a smooth transition therebetween. 15.The controlled motion system of claim 14, wherein the equation-generatedsegment comprises a clothoid curve.
 16. The controlled motion system ofclaim 14, wherein the equation-generated segment comprises a cubicparabolic curve.
 17. The controlled motion system of claim 13, whereinthe modified spline geometry comprises a flattened region around acenterpoint of a 180 degree curve.
 18. The controlled motion system ofclaim 13, wherein the curved track module comprises a 90 degree curve.19. The controlled motion system of claim 13, wherein the curved trackmodule comprises a 90 degree module with a modified spline geometry thatis symmetrical about a 45 degree centerline.
 20. A controlled motionsystem comprising: a curved track module interconnectable with othertrack modules to form a continuous track and comprising a plurality ofindividually controlled electromagnet coils effective for creatingelectromagnetic fields for displacing a mover along the curved trackmodule; wherein the curved track module comprises a modified splinegeometry comprising multiple generators, and wherein the curved trackmodule comprises a 90 degree module with a modified spline geometry thatis symmetrical about a 45 degree centerline.